Safety plug socket



Nov. 8, 1949 H. M. KUHN SAFETY PLUG SOCKET Filed Jan. 1.8, 1946 Patented Nov. 8, 1949 A UNITED STATES PATENT OFFICE Application January 18, 1946, Serial No. 641,965 In Argentina July 26, 1945 13 Claims. (Cl. 1273-330)I This invention relates to certain new and useful improvements in safety plug sockets.

The main object of my invention is to provide an improved plug socket of such construction that closing of the electric circuit therein by means of a nail, wire, hairpin, or like foreign metallic element which is often inserted by children in openings of the socket receptacle is rendered practically impossible; therefore, according to the invention only by means of the complementary pin plug the contact for closing the electric circuit may be established in the plug socket.

One important object of the invention resides in providing an improved two-pin or three-pin plug socket, wherein the pins of the plug do not establish a direct circuit-closing contact, but are so disposed that when the pins will be inserted into the socket, an insulating member is first contacted, and then displaced and by means of this displacement a contact element associated with said insulating member is moved so as to establish a circuit-closing contact with another of said pins. This way it will be readily appreciated that when introducing a nail or the like into my improved plug socket, such nail only contacts one of the aforementioned insulating mem-bers and by no means is enabled to establish an electric circuit.

Another not less important object of my invention consists in providing an improved twopin or three-pin plug socket whose contact elements are associated with insulating members, said contact elements being under' relatively strong elastic force or being subject to the action of relatively strong springs, whereby displacement of said insulating members together with said contact elements is rendered practically impossible by means of a nail, wire', hairpin, or like metallic element of less rigid construction than that of the usual pin plugs.

A further object of my invention is to provide an improved two-pin plug socket equipped with a iirst movable insulating member projecting into the path of a nrst pin of a usual two-pin plug and associated with a r'st elastic or spring-supported contact element for a second pin of said plug, and with a second movable insulating member projecting into the path of a second pin of said plug associated with a second. elastic or spring-supported contact element for said' first pin of said plug;

In addition to these objects, my present invention comprises the arrangement and construction of parts as will be hereinafter more particu- 2 larly described and explained with reference' to the accompanying drawing showing, by' way of examples only, a preferred embodiment of the invention and certain minor deviations thereof.

n said drawingf Figure l is a schematic plan View of the operative parts of my improved plug socket in inoperative condition;

Figure 2 is a similar schematic plan view of the parts of Fig. l in their operativev circuit-closing condition;

Figure 3' is a similar schematic plan View of a preferred' form of arrangement of elastic contact elements' of my improved plug socket;i

Figure 4 is a vertical cross section of my improved pl'ug socket without the pin plug;

Figure 5 is a somewhatschematic vertical cross section snowing a modified arrangement of the insulating members' and' contact elements of my improved plug socket; and Figure 6 is a schematic plan view of my improved plug socket, illustrating a modified embodiment which comprises Referring to the accompanying drawing, the improved plug socket according to my invention comprises' a casing' or receptacle' of insulating material' Il provided' with the usual spaced: opening's or holes 2` for receiving thel pins 3 of the plug lt (see Figure 5). The wall of the receptacle containing said' holes 2' is suitably provided with small tubular extensions 5", as shown in Figure 5, which serve as guide means for the pms 3.

Adjacent the inner ends oi said extensions 5 and positioned in the path of each of the plug pins 3, there isA disposed a small insulating ball 6 movably arranged in such a way that the same is displaced by the respective pin of the plug upon insertion of the latter' into' the' plug socket or casing` The balls 6' are centrally perforated so as to' enable the same to be readily' mounted in a loose manner' on contact elements' T which are in the form' of' elastic wires, rods or' narrow blades of' goodelectrically' conducting material. The balls' 6' may be of any suitable, hard insulating material such as glass, porcelain or a dielectric plastic material, and instead of balls, small disks, cylinders,v or ring-shaped insulating members may be used'. Further, the insulating members 6 may also be xedly connected with the contact elements 1, and finally the arrangement may be such that the saine are constitutedA by projecting portions with insulated surfaces or insulating coatings of said contact elements.

The contact elements 'l near one of their ends 3 are connected with the terminals 8 of the plug socket, as shown more particularly in Figures 3 and 4, whereas their opposite free ends are slightly curved as shown at 'l' and suitably forked (not shown) so as to enable them to establish an efficient electric contact with the pins 3 of the plug. The free ends of the contact elements l extending beyond the terminals 8 (Figure 3) are conveniently so arranged that they exert a pressing spring action upon the insulating members 6, thereby increasing the effect of the elastic contact elements, which tends to keep the same together with said insulating members 6 in their normal inoperative condition shown in Figures 1 and 3, and the elastic force of the contact elements 'I is substantiated by their loop-forming portions 'I".

The elasticity of the contact elements 1 permits the same to be readily moved from their normal inoperative condition as shown in Figure 1 to the operative circuit-closing condition as illustrated in Figure 2, Vwhen the plug is inserted into the plug socket and the pins 3 displace the insulating members i5 and by means of the latter the contact elements l to such an extent that their curved end portions pass through the openings i3 of suitably arranged plates I (see Figures 1 and 2) and establish an eective electric contact with the pins 3.

The arrangement of these contact elements 'l is always such that, for instance, in a two-pin plug socket, as illustrated on the accompanying drawing, the right plug pin 3 contacts with the right insulating member E, displaces the latter and the contact element l associated or connected therewith, but this contact element establishes a circuit-closing contact with the left plug pin 3, whereas this left pin displaces the left insulating member and causes the contact element associated or connected therewith to establish a circuitclosing contact with the rst-mentioned right plug pin. In a three-pin plug socket the arrangement is the same and always such that any of the pins produces the establishment of a circuitclosing contact with another of said pins.

The insulating members 6 are conveniently mechanically connected with their respective contact elements 1, the arrangement being simply such that said insulating members are perforated and that said contact elements are passed therethrough, as schematically indicated on the accompanying drawing, so that the insulating members are loosely mounted on the Contact elements. In Figure 5, the insulating members 6 are iixedly connected in any suitable manner with the contact elements l, because in the arrangement shown in said figure, the plug pins 3 move the insulating members downwards and thereby cause the contact elements 1 to move in the same direction into contact with the pins 3. Finally the arrangement may also be such that there is no mechanical connection between the insulating members t and their respective contact elements As will be readily appreciated, for instance,

. the embodiment as shown in Figure 5 does not necessarily requirea mechanical connection of the insulating members 6 with the Contact elements .'I.

In the embodiments of my invention as shown in Figures 1 to 4 and 6, the insulating members 6 are displaced laterally by the plug pins 3, and

although the same do not necessarily require special supports, I prefer to provide my improved plug socket with an inner wall surface of insulating material 9 adapted to support in corresponding recesses I said insulating members E and to insure that the displacement of the same by said plug pins occurs under right angles with regard to the latter. Similar recesses may also be provided for the contact elements l in the socket portions comprising the holes for the terminal screws 8, as indicated at Il in Figure 4. The afore-mentioned inner wall 9 is held in place by the terminal screws 8 and is provided with projecting plates I4 (Figures 1 and 2) for the purpose as herenbefore already set forth and not only for guiding the contact elements l, but also for preventing the latter from being touched from the outside by means of a bent wire or the like.

Instead of employing elastic contact elements l, as shown in Figures 1 to 5 inclusive, I may also employ movably mounted rigid contact levers 'I (Fig. 6) having as pivots the terminals 8 and provided with relatively strong springs i6 and with suitable stops l2, whereby said contact levers are normally held in their inoperative condition. The operation of the improved plug socket comprising the aforementioned rigid spring-supported Contact elements is the same as that hereinbefore explained.

Referring once more in general to the accompanying drawing, it may be pointed out that in addition to the main embodiment of my invention, the same illustrates as minor alterations possibly to be made in lmy improved plug socket: in Figures l and 2, the guide and protecting plates I for the contact elements l; in Figure 3, the end portions 1 of the contact elements 'l' pressing upon the insulating members 6 and assisting in maintaining the same in their normal position; in Figure 4, the inner or bottomwall 9 and the recesses l0 and H for the insulating members 6 and the contact elements l; a diierent arrangement of the insulating members 6 and of the contact elements l with 'regard to the plug pins 3, being shown in Figure 5, whereas and in Figure 6 the elastic contact elements are replaced by rigid spring-supported contact levers 1.

It will be readily understood that this invention is by no means restricted to the embodiments as shown and described, but that further alterations may be made therein, and that such alterations are to be considered as falling within the scope of my invention as clearly set forth and outlined in the appended claims.

What I claim as new and desire to secure by Letters Patent is:

1. A safety plug socket comprising a receptacle of insulating material having spaced openings for inserting therein the pins of a plug, a plurality of 55 insulating members, a plurality of contact elements, said members and said contact elements being movably connected together and arranged in said receptacle, respective seats in said receptacle for guiding said insulating members, the 60 number of said insulating members and of said contact elements corresponding to that of the pins of said plug, said insulating members being arranged to extend into the path of said plug pins, whereby upon insertion of said plug pins into said e5 plug socket said contact elements will be lmoved by means of the respective insulating members to establish a circuit-closing contactwith said pins,

Y respectively.

2. A safety plug socket comprising a receptacle 10 of insulating material having an inner wall surface and spaced holes for inserting therein the pins of a plug, insulating members, contact elements, said members beingloosely mounted on said contact elements and arranged in said re- 75 ceptacle, and guide means for said insulating s members and positioned on said inner wall surface of said receptacle, the number of insulating members and of said contact elements corresponding to that of the pins of said plug, said insulating members being arranged to extend into the path of the plug pins, whereby upon insertion of said plug into the plug socket said Contact elements will be moved on account of the engagement of said pins with said insulating members for establishment of a circuit-closing contact with said pins.

3. A safety plug socket comprising a receptacle of insulating material having holes for inserting therein the pins of a plug, movable insulating members, movable contact elements operatively connected with said insulating members and provided with free ends out of line with said holes, the number of said insulating members and of said Contact elements corresponding to that of the pins of saidplug, said insulating members extending into the path of said plug pins so that upon insertion of said plug pins into the plug socket said contact elementsr will be moved by means of the respective insulating members for contact with the plug pins whereby one of said pins causes contact of the respective contact element with another of said pins.

4. A safety plug socket having spaced openings for the insertion of a two-pin plug comprising a casing of insulating material, a pair of electric terminals xed to said casing, electric conductors, first and second, respectively, in contact with said terminals, said electric conductors terminating in curved free ends out of line with said openings, respectively, and springedly being mounted for movement to establish electric engagement with said pins, respectively, upon insertion of the latter into said openings, and insulating members operatively connected with said conductors and arranged for position in the path of said openings, respectively, said insulating members when contacted by said inserted pins of said plug moving the free end of said rst conductor into engagement with one of said pins and the free end of said second conductor into engagement with the other of said pins.

5. A safety plug socket having spaced openings for the insertion of a plug carrying two pins, rst and second, respectively, comprising a casing of insulating material, a pair of electric terminals accommodated in said casing, electric conductors, first and second, respectively, in contact with said terminals and spring-supported in said casing, an insulating member connected with each conductor and positioned in the path of a respective opening, said insulating members being engageable with said pins upon insertion of the latter into said openings and being adapted to move said rst conductor into engagement with said second pin and said second conductor into engagement with said first pin, said conductors being provided with curved end portions for abutment with said plug pins, respectively.

6. A safety plug socket having spaced openings for the insertion of a plug carrying two pins, iirst and second, respectively, comprising a casing of insulating material, a pair of electric terminals accommodated in said casing, spring-actuated electric conductors, rst and second, respectively, in contact with said terminals and for electric engagement with said pins upon insertion of the latter into said openings, insulating means connected with each conductor and positioned in the path of a respective opening, said insulating means being engageable with said pins upon insertion of the latter into said openings, whereby said rst conductor is moved into engagement with said second pin and said second' conductor into engagement with said first pin, said conductors being provided with curved end portions for abutment with said plug pins, respectively, said curved end portions being positioned in said casing and out of the plane of said openings upon removal of said pins from the latter.

7. A safety plug socket having spaced openings for the insertion of a plug carrying two pins, first and second, respectively, comprising a casing of insulating material, a pair of electric terminals accommodated in said casing, electric conductors, rst and second, respectively, in contact with said terminals and spring-supported in said casing, an insulating member loosely mounted on each conductor and arranged for position in the path of a respective opening, said insulating members being engageable with said pins upc-n insertion of the latter into said openings and being adapted to move said first conductor into engagement with said second pin and said second conductor into engagement with said rst pin, said conductors being provided with curved endv portions for abutment with said plug pins, IGSDSCVGIY 8. A safety plug socket having spaced openings for the insertion of a plug carrying two pins, first and second, respectively, comprising a casing of insulating material, a pair of electric terminals accommodated in said casing, spring-actuated electric conductors, first and second, respectively, in Contact with said terminals and for electric engagement with said pins upon insertion of the latter into said openings, insulating means carried by each conductor and positioned in the path of a respective opening, said insulating means being engageable by said pins upon insertion of the latter into Said openings and being adapted to move said first conductor into engagement with said second pin and said second conductor into engagement with said first pin, said conductors being provided with curved end portions for abutment with said plug pins, respectively, said curved end portions being positioned in said casing and out of the plane of said openings upon removal of said pins from the latter, and means within the connes of said casing for guiding said insulating members during movement thereof.

9. A safety device of the character described comprising a casing having a plurality of openings, a plug having a plurality of pins for insertion in said openings and connection of said plug with said casing, a plurality of connectors springedly supported within said casing and provided with respective insulating portions, said insulating portions being positioned in the path of said openings and being guidingly displaceable within said casing against the spring action of said connectors, said connectors terminating in free ends, respectivelyy and guide means for said insulating portions within said casing, whereby upon insertion of said pins in said openings each one pin displaces the insulating portion of the respective connector to establish electric contact between the respective free end of one of said connectors with another said pins, while the insulating portion of the respective connector is guided along the respective guide means.

l0. In a safety plug socket provided with electric terminals and openings for the insertion of the pins of a plug; the combination of electric conductor means connected to said terminals,

respectively, and provided with contact portions arranged for movement relatively to said terminals, with insulating means arranged in the path of said openings in inoperative position of said contact portions and operatively connected with said conductor means, respectively, said contact portions being disposed in inoperative position out of alignment with said openings, whereby upon insertion of said pins of said plug in said openings of said socket said insulating means are movable from inoperative position to operative position in which said contact portions of said conductor means, respectively, engage said pins of said plug.

11. In a safety plug socket according to claim 10, wherein said conductor means extend in cross- Wise relation to each other from said terminals,

whereby said contact portions of said conductor means are adapted to engage pins of said plug other than those which move the respective insulating means. Y

12. In a safety plug socket according to claim 10, wherein said insulating means form coatings on said conductor means, respectively.

13. A safety plug socket comprising a receptacle of insulating material having an open end and at least two openings for inserting therein the pins of a plug; electric terminals secured in place within said receptacle; a plate for closing the open end of said receptacle and fixed in place by said terminals; at least one pair of electric conductors connected with and for movement relatively to said terminals; atleast one pai of insulating members mounted for displacement on said conductors and normally in the path of the openings of said receptacle, said insulating members being adapted to move said conductors to circuit-closing contact With said pins upon insertion of the latter in said openings, said conductors being provided with contact portions for engaging said pins and being arranged in crosswise relation to each other for contacting' a pin other than that displacing the respective insulating member; and at least one pair of recesses formed on said plate for guiding said insulating members during their displacement caused by the inserted pins.

HEDWIG MARGARITA REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,224,366 Johnston Dec. l0, 1940 2,263,630 Johnston Nov. 25, 1941 FOREIGN PATENTS Number Country Date 374,145 Italy Aug. 16l 1939 435,330 Great Britain Sept. 19, 1935 467,743 Great Britain June 23, 1937 

